Originally Posted by Tones Teo
I don't mean to sound ignorant guys & please correct me - (1/4 mile bunny)
Isn't the idea to shift at or close to where the engine makes max torque for optimum acceleration???
The general idea is to shift just beyond peak torque to the degree that the engine loses the minimum amount of RPM (RPM drop is lowest) through the gear change.
On a gear change, the engine will drop RPM. That's expected. What we want to do is relocate the RPM in the band where it will continue to pull strongest. Most vehicles use a fairly wide ratio transmission. This ensures that there will be a significant RPM drop on every gear change, whether manual or auto.
The killer thing for us is to have a six speed instantly shifting automatic transmission that keeps the RPM rise and fall to about 1000 RPM right in our peak torque band...but that isn't very practical, affordable or even reasonably feasible...is it? So we use camshafts, tire sizes, differential gears and stall converters to give us the strongest possible lauch and top speed for the RPM range that our engines have once built.
The engine dyno, even a "Desktop" dyno will tell us the effective RPM band for an engine with detailed information about that engine. Chassis dynos will show us where our engine pulls in our particular combination and what RPM band it favors. There is some potential benefit by slightly exceeding the top end of that band during gear changes, but certainly not to the point of floating the valves, which is always a no-no.
The bottom line tends to be what works best at the track versus what sounds good on paper. As every combination is different, it is unlikely that there is an easy answer to the question without some simple hardware.
Basically, what you want to do in the car to really test the most effective gear change RPM is to use an accelerometer with feedback. Once your acceleration rate increase drops, you want to change gears.